Odd-coordinate kernel conjecture for singular io-decomposable Riordan graphs

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Let Gn(g,zg)G_n(g,zg) be a singular io-decomposable Riordan graph, let An{\cal A}_n be its adjacency matrix, and let X=[x1,x2,…,xn]TX=[x_1,x_2,\ldots,x_n]^T be an eigenvector with eigenvalue 00. Define the odd-index and even-index subvectors by

Xo=[x1,x3,…,x2⌈n/2⌉−1]T,X_o=[x_1,x_3,\ldots,x_{2\lceil n/2\rceil-1}]^T, Xe=[x2,x4,…,x2⌊n/2⌋]T.X_e=[x_2,x_4,\ldots,x_{2\lfloor n/2\rfloor}]^T.

Odd-coordinate kernel conjecture. Then

Xo=O⌈n/2⌉.X_o=O_{\lceil n/2\rceil}.

This claim is motivated by Sage computations and, together with the preceding block-matrix lemma, would constrain the zero-eigenspace of every singular io-decomposable Riordan graph. No proof or resolution is supplied.

References

Primary source

Gi-Sang Cheon, Ji-Hwan Jung, Sergey Kitaev and Seyed Ahmad Mojallal, “Riordan graphs II: Spectral properties”, arXiv:1801.07021 (2018).

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